Catheters are commonly used invasively to treat diseased vessels in animal and human bodies. Cardiovascular diseases are one of the most common diseases treated by the use of catheters. Catheters are used to counter atherosclerosis, one of the effects of cardiovascular disease, through a procedure known as balloon angioplasty wherein a balloon is inflated in the diseased vessel at a location where a narrowing of the vessel has occurred.
It will be appreciated, that in addition to angioplasty, there are numerous other uses of catheters in a living being such as treatment of the urinary tract, brain, lungs, kidneys, liver, etc.
In some of these treatments, it is often necessary to have a relatively long term occlusion due to angioplasty balloon inflation within a body vessel, which prevents fluid flow through the vessel externally of the catheter. For example, it is not uncommon to have a blockage, due to inflation of the catheter balloon, occurring for more than ten seconds. In certain situations, such as severe coronary artery disease, no interruption of blood flow can be safely tolerated.
For this reason, perfusion catheters have been constructed which are adapted to pass blood through the catheter even though the catheter is acting to block flow externally to the catheter in the area of the vessel which is being treated, multiple areas of the vessel being treated in some situations. Perfusion catheters are of two general types. Perfusion balloon catheters have an inflatable angioplasty balloon attached and are typically used to enable perfusion of blood through the catheter when the angioplasty balloon is inflated during vessel dilation. Perfusion "bailout" catheters do not have a balloon attached and are typically used in emergency situations when there is a vessel dissection or tear post angioplasty. Perfusion "bailout" catheters have proximal and distal side-holes and function as a temporary stenting device to hold the vessel open until the patient is otherwise treated, such as by emergency bypass surgery.
Typical perfusion catheters have one or more simple apertures upstream of the treatment or blockage site, and one or more apertures downstream. See for example, U.S. Pat. No. 4,581,017, FIG. 2. Such catheters have a rate of flow though that is primarily controlled by the diameter of the flow lumens within the catheter, the pressure difference across the lumens, viscosity of the fluid used, the length of the catheter tube, etc. These perfusion catheters often do not provide the high fluid flow rate required through the vessel during the blockage by the catheter balloon. As a result, treatments requiring a more extended blockage of the vessel are risky, since even with the perfusion provided, the flow downstream of the catheter is less than the needed flow. The blood pressure may also be too low to support good flow.
U.S. Pat. No. 4,857,054 discloses an attempt to overcome this problem. This patent discloses a perfusion angioplasty catheter with pump assist. The catheter includes a tube having a distal end including means for effecting angioplasty treatment of a body vessel, and a proximal end containing control means. The tube of the catheter further includes a perfusion lumen extending most of the length of the tube and means in the tube adjacent the distal end defining a plurality of apertures, on both sides of the catheter balloon, providing for fluid movement from or to the lumen past the balloon. The catheter includes a plurality of one way valves each disposed proximate one of the apertures. At least one of the valves is constructed to admit fluids only into the lumen from the body vessel and at least one of the other valves being constructed to permit fluid only to the body vessel from the lumen. The control means is located external of the body and controls a pump which is also external of the body for pumping a fluid such as a saline solution or a blood substitute into the perfusion lumen. As the pump pumps fluid into the perfusion lumen, blood is forced out of the perfusion lumen and into the body vessel. As the pump withdraws the fluid, blood is caused to flow into the perfusion lumen. In this fashion, the pump assists blood flow through the catheter around the obstructed site in the body vessel. Some disadvantages associated with this design is that fluid flow can only occur in one direction. Moreover, the pump is on the outside of the body. Also, the relatively long fluid flow path and the fluid viscosity, would seem to make it difficult to ensure adequate fluid flow.
The present invention solves many of the problems associated with current perfusion catheter systems.